Preparation And Characterization Of Hydrophilic And Antibacterial Dual-functional Modified Ultrafiltration Membrane With Quaternized Graphene Oxide

Polyvinylidene fluoride(PVDF)is widely used as a kind of ultrafiltration membrane materials with excellent performance.However,because of the limitations of the material properties itself,it easily adsorbs organic matter and bacteria and other pollutants from the raw liquid when it is prepared into an ultrafiltration membrane for water treatment.The formation of more severe membrane biological pollution on the membrane surface affects the service life of the ultrafiltration membrane.Therefore,the preparation of a PVDF ultrafiltration membrane with hydrophilic and antibacterial dual properties is very significant in current development and application.In this study,graphene oxide(GO)was selected as the raw material of the membrane modifier.The hydrophobic carbon skeleton is easily entangled inside the polymer membrane material,which can reduce the loss in the water treatment process effectively.The hydrophilic groups such as hydroxyl groups on its surface can make the GO more easily enriched at the membrane-water interface.The GO also has a number of carboxyl groups and epoxy groups,which can be used as an active site to graft other functional groups.Quaternized graphene oxide(QGO)with hydrophilic antibacterial properties was prepared by growing quaternary ammonium salt groups with high antibacterial activity in situ on the surface of GO nanomaterials.The preparation process was screened and optimized progressively,and finally the best synthetic process conditions were determined.The changes of nanomorphology and element distribution were observed by transmission electron microscopy.The infrared spectroscopy,X-ray photoelectron spectroscopy and X-ray diffraction to determine the changes of functional group composition and chemical properties.The bleed situation and antibacterial properties were also tested and characterized.The characterization results showed that the QGO nano-material which uniformly loaded with quaternary ammonium salt groups was successfully prepared,and it still maintained the nano-sheet structure of GO.QGO also had good dispersibility and stability in different solvents.The quaternary ammonium salt groups in QGO were hardly lost in water treatment,so QGO showed the long-lasting and stable antibacterial activity.QGO was blended into PVDF as a film material modifier,and a quaternized graphene oxide modified PVDF ultrafiltration membrane(QGM)with hydrophilic and antibacterial properties on the surface was prepared by immersion phase inversion method.The optimal preparation conditions were screened by optimizing PVDF addition amount and coagulation bath conditions.The chemical structure of the membrane was characterized by infrared spectroscopy,and the changes in the microstructure of the membrane were observed by scanning electron microscope and atomic force microscope.By characterization of water contact angle and mechanical properties,it was shown that the modified membrane has better hydrophilic properties and mechanical strength.Finally,through the filtration performance test and the antifouling and antibacterial test,it was found that the modified membrane has better permeability and excellent antifouling and antibacterial performance.Meanwhile,its hydrophilic antibacterial group was not easy to lose,which effectively improves the resistance to biofilm pollution.Based on these,an ultrafiltration membrane material with long-term stable hydrophilic antibacterial properties was constructed..